"Ride the Tiger" characterizes JFK as being "undisciplined, out-of-control and an adrenaline freak," says the playwright. In the play's first scene Joe Kennedy, a formidable planner who envisions a 100-year dynasty for his sons and their offspring, warns his son about his problem.

"The Kennedys cut Frank out, too," says Mastrosimone, "and that infuriated Sam who felt like he looked like a fool in front of his people — and foolish means weak and that means there's danger to his own life from his own people.

"Sam said to Frank: 'Joe knows who I am but his kids think I'm the Boy Scouts. They don't appreciate that I am a powerful man.' The last thing he said to Frank was, 'We're going to show those two brothers how the Boy Scouts keep score."

JFK was killed in 1963; his brother Robert in 1968, though Mastrosimone says the mob link to RFK's assassination is not strong. Giancana's relationship with the CIA — he was involved since the late '50s in plots to kill Cuba'sFidel Castro — has fueled a conspiracy theory about the presidential assassination.

That theory was bolstered beginning in January, 1975, when a senate committee was created, headed by U.S. Sen. Frank Church, a Democrat from Idaho, to investigate CIA and Mafia ties.

Prior to testifying, Giancana was killed June 19, 1975, in his Chicago home, from gun shots to the back of his head and in the mouth — the latter seen as a warning against talking.

Mastrosimone believes that Giancana knew his killer because the table was set for two and sausages and peppers were simmering on the stove. The writer is not sure whether the murder was a mob hit or done by the CIA.

Mastrosimone remembers a telling transcript of a wiretap at a restaurant where Giancana and another mobster were meeting. When the other mobster, who was just indicted, asked him what to do, Sam pointed to a stuffed marlin hanging on the wall. 'You see that fish up there? The only way it got caught was when it opened its [expletive] mouth.'

Power of Beauty

And as for party girl Exner who linked Kennedy and Giancana?

Compared to the other characters, "she looks like an ant next to giants," he says. "But her power was that of the Geisha Girl — the power of beauty, being subservient and possessing the ability to stop a man in his tracks with a glance. She understood that powerful men don't want powerful mistresses. They want malleable people.

"But there are things that she wants. She believes that Jack loves her and she has a future. She believes she can be First Lady, though she never says that. Still, she fights for that in her own way."

Exner wrote her own memoir in 1977 entitled, "My Story."

"I don't buy her version at all," says Mastrosimone. "It's laughable. I think she wrote that book after Sam was murdered to tell the Mafia, 'Look, I have a chance to spill the beans and I'm not going to do it. In fact, I'm going to entertain you with all this [b.s.] and lie and you will see you have nothing to fear from me.' I believe she was truly fearful for her life." Exner died in 1999 at the age of 65. Joseph Kennedy suffered a stroke in 1961 and died in 1969, living long enough to see two sons assassinated. Sinatra died in 1998 at the age of 82.

Though Mastrosimone thought Exner's version was a protective concoction he believes the behind-the-scenes story Sinatra told him for two reasons.

"When we talked about JFK his eyes welled up. He was still smarting from the betrayal 25 years later. But there was an even greater reason why I believed him. The story he told made him look bad. That tough Sinatra of popular propaganda is not in this play. In this play he gets pushed around. He's humiliated. So why would he tell this story? Because he wanted the truth to be told."

Does Mastrosimone have any fear of retribution for telling this story?

"It would look good on my resume if I ended up like Johnny Roselli in a 50-gallon drum filled with cement," he says with a small smile of the mobster known as "Handsome Johnny," a friend of Sinatra's who was called twice to Church's committee. "But the mentality of the mob has changed. They would be proud of this."

And finally, the meaning of the title of the play?

Mastrosimone says it came from Kennedy's inaugural address in which he warned countries who were gravitating toward Communism.

"Once you are riding the tiger," says Mastrosimone, paraphrasing Kennedy, "the problem comes in the dismounting."

RIDE THE TIGER runs through April 21 on Long Wharf's main stage, 222 Sargent Drive, New Haven. Tickets are $42 to $72. Information: 203-787-4282 and http://www.longwharf.org.

Read Frank's blog on theater, the arts and entertainment at http://www.courant.com/curtain. And be the first to know by following him on Twitter at http://www.Twitter.com/ShowRiz.